J. Michael Selbach

Episcleral Venous Pressure in Untreated Primary Open-Angle and Normal-Tension Glaucoma

The aim of this prospective study was to investigate episcleral venous pressure (EVP) in different forms of glaucoma in comparison with age-matched controls. EVP was measured by means of a venomanometer in 32 eyes with untreated primary open-angle glaucoma (POAG), 36 eyes with untreated normal-tension glaucoma (NTG) as well as 56 control eyes without ophthalmological disease other than cataract. In addition to ophthalmological standard examination, cardiovascular parameters such as systolic and diastolic blood pressure and heart rate were recorded. In the POAG group, EVP was 12.1 ±0.5 mm Hg and in the NTG group 11.6 ± 0.4 mm Hg. This was significantly different from EVP of the controls (9.5 ± 0.2 mm Hg). The EVP/intraocular pressure (IOP) ratio was significantly different in NTG patients (80.0% ± 3.2) in comparison with both POAG patients (67.1% ± 2.8) and controls (69.2% ± 2.4). The difference between IOP and EVP (IOP – EVP) was 6.2 ± 0.6 in the POAG, 3.1 ± 0.45 in the NTG and 4.5 ± 0.4 in the control group. All these values were significantly different from each other. Regression analysis revealed a significant linear correlation between EVP and IOP in both the NTG and the POAG group. In the control group, however, the correlation was weak. This study is the first to demonstrate differences in EVP between untreated NTG and POAG and an age-matched healthy control group.

Angioarchitecture and innervation of the primate anterior episclera.

Purpose: To investigate the primate episcleral vasculature and its innervation with respect to morphological specializations. Methods: Serial sections of the anterior episclera of 8 monkey eyes and 20 human eyes were investigated enzyme- and immunohistochemically using antibodies against smooth-muscle α -actin (SMA), neurofilament, synaptophysin, substance P (SP), calcitonin gene-related peptide (CGRP), vesicular acetylcholine transporter (VACHT), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), tyrosine hydroxylase (TH), vesicular monoamine transporter II (VMAT II), as well as the NADPH-diaphorase reaction. Arteriovenous anastomoses (AVA) were quantified. Results: All episcleral vessels including veins showed intense staining for SMA. Capillary loops were only seen in the limbal arcades, not in the episclera itself. Instead, AVA connected the episcleral arteries with the veins, which formed an interlacing vascular network. In the monkey episclera, 4–6/mm2 AVA were found; in the human episclera, 0.5–1/mm2. Numerous nerve endings staining for NADPHd (NADPHdiaphorase) and TH surrounded all episcleral vessels including anastomoses and veins. NPY, VIP, and VACHT-immunoreactive (IR) nerve terminals were less numerous. CGRP and SP-IR terminals were seen both at the vessels and in the intervascular connective tissue. Conclusions: The episcleral vasculature shows a specialized morphology with absence of capillaries, numerous arteriovenous anastomoses, a muscle-rich venous network, and intense innervation by vasodilative and vasoconstrictive nerves. This might allow regulation of blood flow and volume in the episcleral vessels and Voigts capillaries for thermoregulation and modulation of episcleral venous pressure and thereby outflow facility.

Substance P and opioid peptidergic innervation of the anterior eye segment of the rat: an immunohistochemical study

Recently discovered endogenous opioid peptides such as nociceptin are known to modulate neurotransmitter release of primary afferent neurons (especially substance P, SP) and they have also been demonstrated in peripheral nerve fibres. The aim of this study was to investigate the opioid peptidergic innervation of the anterior eye segment and to compare it with the innervation pattern of SP in order to shed light on the functional relationship between these peptides. Anterior eye segments of 20 rat eyes were cut in a tangential plane and the sections stained with antibodies against SP, nociceptin, nocistatin, endomorphin 1 and 2, leu‐enkephalin and met‐enkephalin. Sections of the spinal cord or brain were used as positive controls. Numerous SP‐immunoreactive nerve fibres were found in the conjunctiva, cornea, episclera, trabecular meshwork, iris and ciliary body. A weak staining for met‐enkephalin and leu‐enkephalin could only be found in the iris and anteriormost ciliary body. Nerve fibres immunoreactive for nociceptin, nocistatin, and endomorphin 1 or 2 could not be detected in any part of the anterior eye segment. It is tempting to speculate that the opioid peptidergic innervation of the anterior ciliary body may play a role in the modulation of intraocular inflammation.

Scanning Laser Topography and Scanning Laser Polarimetry: Comparing Both Imaging Methods at Same Distances from the Optic Nerve Head

Purpose: To compare the performance of scanning laser topography (SLT) and scanning laser polarimetry (SLP) on the rim of the optic nerve head and its surrounding area and thereby to evaluate whether these imaging technologies are influenced by other factors beyond the thickness of the retinal nerve fiber layer (RNFL). Materials and Methodology: A total of 154 eyes from 5 different groups were examined: young healthy subjects (YNorm), old healthy subjects (ONorm), patients with normal tension glaucoma (NTG), patients with open-angle glaucoma and early glaucomatous damage (OAGE) and patients with open-angle glaucoma and advanced glaucomatous damage (OAGA). SLT and SLP measurements were taken. Four concentric circles were superimposed on each of the images: the first one measuring at the rim of the optic nerve head (1.0 ONHD), the next measuring at 1.25 optic nerve head diameters (ONHD), at 1.5 ONHD and at 1.75 ONHD. The aligned images were analyzed using GDx/NFA software. Results: Both methods showed peaks of RNFL thickness in the superior and inferior segments of the ONH. The maximum thickness, registered by the SLT device was at the ONH rim where the SLP device tended to measure the lowest values. SLT measurements at the ONH were influenced by other tissues besides the RNFL like blood vessels and glial tissues. SLT and SLP were most strongly correlated at distances of 1.25 and 1.5 ONHD. Conclusions: While both imaging technologies are valuable tools in detecting glaucoma, measurements at the ONH rim should be interpreted critically since both methods might provide misleading results. For the assessment of the retinal nerve fiber layer we would like to recommend for both imaging technologies, SLT and SLP, measurements in 1.25 and 1.5 ONHD distance of the rim of the optic nerve head.